Inkling takes textbooks and other content from publishers, and rebuilds each title from the ground up into cross-platform, interactive experiences. Indeed, Inkling’s offerings also covers the likes of cookbooks and Frommer’s travel guides, creating pocket-friendly versions of well-known titles.

During the last school year, Inkling says that more than 4,000 schools’ students used the service in some form. Now, with their textbooks available on iPhone/iPod Touch, in addition to the existing iPad, PC and Mac versions, students can watch videos, spin molecules and take quizzes anywhere.

“This is the first time anyone has shrunk complex content like textbooks down for iPhone and made it work beautifully,” says Matt MacInnis, CEO of Inkling. “For every iPad user, there are four iPhone users, so Inkling for iPhone brings the Inkling experience to a broader universe of people.”

Assessments with responsive scoreboards to track how you’re doing as you go.

Quick chapter downloads. Users can download one chapter at a time, if space is limited on your device.

Inkling for iPhone/iPod Touch works with Inkling Habitat too, which is its professional-grade publishing platform.

“We’re now the world’s only publishing platform for interactive content on phones, tablets and the web,” added MacInnis. “With every release, we’re tackling the publishing industry’s most pressing problem: how to produce truly engaging, interactive content experiences cross-platform and at scale.”

Based in San Francisco, Inkling is backed by Sequoia Capital and other key partners from some of the world’s preeminent educational and trade publishers.